# Transformer layers direction

Discussion in 'General Electronics Discussion' started by nebojsa, Apr 21, 2019.

1. ### nebojsa

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May 13, 2017
I have to wind a transformer core.
There will be 3 x 7 windings.
What I dont know is:
When I wind first 7 windings from one end to another
should I:
A/ back wire diagonaly/straight across first 7 windings to the start end and start second 7 windings again in same direction and repeat the same for third 7 windings
B/ start second 7 windings from that end but in opposite direction
Sorry for bad english, I hope this was understandable...

2. ### duke37

5,364
771
Jan 9, 2011
I think that there could be some confusion on what you want to do. I use the term winding to mean the assembly of turns connected together so, a transformer would have a 6.3V winding.
Do you mean that you have 3 windings, each of 7 turns. Are they connected in series or isolated from each other?

I am no expert on transformer winding but you should try and get a level surface for a subsequent winding. If a connection is to go across from one side to the other, then make sure the bulge is placed so that it does not interfere with the laminations.
You wind on a bobbin, not on a core unless it is a toroid.

There is a very good web site by Ludens which descibes how to wind transformers

3. ### duke37

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Jan 9, 2011
ludens.cl/Electron/trafos/trafos.html
Practical transformer winding . In the good old times it was a matter of fact that every electronic hobbyist or technician would wind himself any power transformers he needed, and rewind any that burned out.

4. ### Minder

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Apr 24, 2015
Any sets of windings that are intended to be identical, in most cases are wound bi-filar, or together, to achieve the identical windings
M.

5. ### nebojsa

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May 13, 2017
Hmm, I maybe used wrong terms. 3x7 windings I mentioned is one secondary coil. Core of transformer is square (cube, better to be said) of midle E type core. Wire is 3 mm in diameter and core height is 22 mm, so there can be only 7 turns fitted( or windings, but this is maybe wrong term). Wnen first 7 turns are wraped (maybe again wrong term) what should I do? If I wind second 7 turns from that end it will change direction (clockwise to counterclockwise). Is this wrong or not?

6. ### BobK

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1,688
Jan 5, 2010
It is okay to wind the first layer from left to right, then the next from right to left. That does not change the direction (CW/CCW.). If you do change the direction of the winding, the twio layers would cancel each other out.

Bob

7. ### nebojsa

40
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May 13, 2017
That means B answer? But without word ''opposite''. Its the same direction, if I got it right...

8. ### duke37

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771
Jan 9, 2011
So you have one winding of 21 turns, tapped at 7 turns and 14 turns.
It seems as if 7 turns can be accommodated in one layer on the bobbin which is 22mm wide. Thus you should start at one side, put on 7 turns then take out a tap at the opposite side. Continue winding in the same direction but traverse back to the start side. Take out another tap then put on your third layer. If you do it this way, you will not need to put a tap wire across the existing winding making a much neater result.

The start, finish and taps must be on the bobbin sides which do not interfere with the laminations.

Mark the connections, the resistance will be very low so it may be difficult to identify them later with an ohm meter. The taps should be obvious since they will be a loop.

The layers will have opposite helix directions and it may be easier to put some insulation over the first layer to give a flatter surface for the next layer.

9. ### BobK

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Jan 5, 2010
There are no taps, he is just doing a single winding of 21 turns in 3 layers.

Bob

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10. ### Bluejets

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Oct 5, 2014
I took this to be 3 separate windings.......????

Ahh..ok..see it now "3x7 windings I mentioned is one secondary coil"

Last edited: Apr 23, 2019
11. ### BobK

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Jan 5, 2010
He was using the term "windings" when we would say "turns".

Bob

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12. ### Bluejets

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Oct 5, 2014
Depends which side of which ocean one lives on I guess.